Used packing when laying marshalling structures out sequentially.

Fixes https://github.com/mono/CppSharp/issues/772.

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/CppParser/Parser.cpp

@@ -3820,7 +3820,7 @@ Declaration* Parser::WalkDeclaration(const clang::Decl* D,
             if (Attr->getKind() == clang::attr::Kind::MaxFieldAlignment)
             {
                 auto MFA = cast<clang::MaxFieldAlignmentAttr>(Attr);
-                Decl->maxFieldAlignment = MFA->getAlignment();
+                Decl->maxFieldAlignment = MFA->getAlignment() / 8; // bits to bytes.
             }
         }
     }

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -428,7 +428,8 @@ namespace CppSharp.Generators.CSharp
             PushBlock(BlockKind.InternalsClass);
             if (!Options.GenerateSequentialLayout || @class.IsUnion)
                 WriteLine($"[StructLayout(LayoutKind.Explicit, Size = {@class.Layout.Size})]");
-            // no else because the layout is sequential for structures by default
+            else if (@class.MaxFieldAlignment > 0)
+                WriteLine($"[StructLayout(LayoutKind.Sequential, Pack = {@class.MaxFieldAlignment})]");
 
             GenerateClassInternalHead(@class);
             WriteStartBraceIndent();

tests/Common/Common.Tests.cs

@@ -620,6 +620,23 @@ public class CommonTests : GeneratorTestFixture
         Assert.IsFalse(differentConstOverloads == 5);
     }
 
+    [Test]
+    public void TestPacking()
+    {
+        foreach (var testPacking in new TestPacking[] { new TestPacking1(), new TestPacking2(),
+            new TestPacking4(), new TestPacking8() })
+        {
+            testPacking.I1 = 2;
+            testPacking.I2 = 4;
+            testPacking.B = true;
+
+            Assert.That(testPacking.I1, Is.EqualTo(2));
+            Assert.That(testPacking.I2, Is.EqualTo(4));
+            Assert.That(testPacking.B, Is.EqualTo(true));
+            testPacking.Dispose();
+        }
+    }
+
     [Test]
     public void TestRenamingVariableNamedAfterKeyword()
     {

tests/Common/Common.cpp

@@ -1,6 +1,42 @@
 #include "Common.h"
 #include <string.h>
 
+TestPacking::TestPacking()
+{
+}
+
+TestPacking1::TestPacking1()
+{
+}
+
+TestPacking1::~TestPacking1()
+{
+}
+
+TestPacking2::TestPacking2()
+{
+}
+
+TestPacking2::~TestPacking2()
+{
+}
+
+TestPacking4::TestPacking4()
+{
+}
+
+TestPacking4::~TestPacking4()
+{
+}
+
+TestPacking8::TestPacking8()
+{
+}
+
+TestPacking8::~TestPacking8()
+{
+}
+
 Foo::Foo()
 {
     auto p = new int[4];

tests/Common/Common.h

@@ -7,24 +7,46 @@
 #include <string>
 #include <vector>
 
-#pragma pack(4)
-class TestPacking
+class DLL_API TestPacking
 {
 public:
-    int integer;
-    bool boolean;
-    double dble;
+    int i1;
     int i2;
+    bool b;
+    TestPacking();
+};
+
+#pragma pack(1)
+class DLL_API TestPacking1: public TestPacking
+{
+public:
+    TestPacking1();
+    ~TestPacking1();
 };
 
 #pragma pack(2)
-struct TestP 
+class DLL_API TestPacking2: public TestPacking
 {
-    char b;
-    bool c;
-    double d;
+public:
+    TestPacking2();
+    ~TestPacking2();
 };
 
+#pragma pack(4)
+class DLL_API TestPacking4: public TestPacking
+{
+public:
+    TestPacking4();
+    ~TestPacking4();
+};
+
+#pragma pack(8)
+class DLL_API TestPacking8: public TestPacking
+{
+public:
+    TestPacking8();
+    ~TestPacking8();
+};
 
 class DLL_API IgnoredType
 {